Hepatitis C virus and Mycobacterium tuberculosis are each immensely successful pathogens, with the common thread between them that host cellular immune responses are extremely important in controlling infection. Our group has made novel genetic modifications to eliminate immune-evasive genes in the most commonly administered worldwide vaccine, BCG. The modified BCG vaccine, called "pro-apoptotic BCG", demonstrates potent immune responses in susceptible mouse strains. Compared to the parent BCG vaccine, the new vaccine elicits greater IL-2 production by T-cells during the primary response to vaccination and quicker recall responses during re-challenge. Our goal with this R21 application is to introduce HCV antigens into these modified BCG strains to develop a hybrid TB-HCV vaccine capable of eliciting potent cellular immune responses. We will 1) Construct recombinant pro-apoptotic BCG (rpaBCG) vaccines that express HCV antigens. 2) Verify recognition of vaccine-expressed HCV antigens by T cell clones and peripheral blood mononuclear cells previously isolated from chimpanzees with chronic or resolved HCV infection. 3) Evaluate immunogenicity of these vaccines in HLA Class I-transgenic mice. If successful, our future goals will include larger scale mouse studies, and small primate studies to evaluate the immunogenicity of vaccines with different HCV inserts. The advantage of pro-apoptotic BCG as a platform for antigen delivery is its ability to elicit stronger immune responses than BCG despite modifications which make it more attenuated, which should also improve upon an already good safety profile in humans. This proposal will take advantage of the unique expertise of each investigator. Our plan to express HCV antigens in a highly immunogenic and safe vector will facilitate the migration of this vaccine from the bench to the clinic. Project Narrative: Hepatitis C virus currently infects 170 million people worldwide, and is a leading cause of cirrhosis of the liver. Our goal is to incorporate Hepatitis C proteins in a modified version of a widely used and safe tuberculosis vaccine, which we call "pro-apoptotic BCG". Our modified BCG vaccine elicits better immune responses in a mouse model than the original BCG strain, and as a combined pro-apoptotic BCG-HCV vaccine could move quickly from testing in mice to humans.